Multifunctional IP6-PAMAM-GL13K conditioning for durable wet and dry resin-dentine bonding

To synthesise and evaluate a high-molecular-weight IP6-PAMAM-GL13K (IPG) dentin bonding conditioner designed to remove extrafibrillar minerals selectively, preserve intrafibrillar mineral, suppress endogenous proteolysis and provide antibacterial activity.

The IPG molecule was characterised by ATR-FTIR, proton NMR, ¹³C NMR and gel permeation chromatography. Calcium chelation was quantified by ICP-AES. Microtensile bond strength was used to determine the optimum concentration and conditioning time and to compare wet and dry bonding before and after 10,000 thermocycles. FE-SEM and AFM were used to examine conditioned dentine. In situ zymography was used to evaluate gelatinolytic activity. Live/dead staining was used to evaluate Streptococcus mutans, Actinomyces naeslundii, and Enterococcus faecalis, and CCK-8 testing was used for examining cytocompatibility.

The IPG conditioner chelated calcium in a concentration- and time-dependent manner. Conditioning with 50 mg/mL IPG for 60 s produced bond strengths comparable with phosphoric-acid and IP6 wet bonding. Bond strength of IPG-etched dentine did not decrease significantly after thermocycling in either wet- or dry-bonding mode. FE-SEM showed preserved mineralised collagen fibrils and extrafibrillar spaces after IPG conditioning, including after air drying. AFM showed greater roughness than phosphoric-acid conditioning. Gelatinolytic activity was 6.5 ± 1.4% for IPG and 84.5 ± 5.2% for phosphoric acid. The IPG increased bacterial killing of all three species and maintained high cell viability at 20-50 mg/mL.

The IPG conditioner enabled selective extrafibrillar demineralisation, stable wet and dry bonding to dentine after thermocycling, low gelatinolytic activity and antibacterial effects.

A multifunctional IPG conditioner may permit dry dentine bonding while preserving bond stability.